What version of FM are you using? 13 has an active state to the portal row. You can select a color for the active row and / or the alternate row. if you activate those in the Portal set up dialog, then going to the inspector, you select the whole portal and choose the "Portal: Row: and "Active Row" to pick the color for that active portal row.
It is possible to do it in 12 or earlier, but not nearly as easy as 13!
Step by step in 13:
1. Select the portal w/ a double-click. Bring up the portal setup dialog.
2. Click on "Use Active Row State"
3. Keep the portal active. Go to inspector.
4. Click on the appearance panel
5. Under the style section (the top) click on Portal. Select Portal: Row
6. Just below that, click on "Active "
7. Choose colors for the active row.
8. Go to browse mode. Check it out!
I am a newbie also. My understanding is that when you access a Layout or a Portal by clicking on a Tab, no row is selected, so no row is highlighted.
Then you need a script to select for example the first row, and magically the row will be highlighted. To do so, in the Inspector, you need to giave a name to your portal (Position Tab, Name field). Then create a script:
Go to Object [ObjectName: "TheNameGivenToThePortal"]
Go to Portal Row [Select; First]
This script is minimal, it does check if there are rows so does not handle an error if now there are no rows.
Note this in FileMaker 12.
That's what I was looking for. I am using FM13.